The invention relates to a wearing ring, particularly for protecting a cable guidance tube on a robot.
Such wearing rings are positioned at critical points of a protective tube for cables on machines, particularly a robot, in order to prevent damage to the protective tube by rubbing or abrading at such critical points, such as points where it can contact moving robot parts, such as a rocker, arm or hand. As the wearing rings are located at critical points, they can themselves be worn away. This is often not frequently sufficiently well observed, so that the danger exists that following the wearing through of the wearing ring the protective tube is also damaged, especially if the wearing ring and tube has inconspicuous colours, particularly the same colouring.
The wearing rings generally comprise two half-shells, which are interconnected by metal screws. If the wearing ring is worn away in the vicinity of the screw fastening, then the countersunk screw heads appear and can then damage robot parts along which rub the wearing rings and therefore the projecting screw heads. Finally, frequently a one-piece tube is not desired and used and instead the protective tube consists of at least two parts, namely parts with different elasticity. They have to be interconnected by additional coupling sleeves, which increase costs.
Whilst avoiding the aforementioned disadvantages, the problem of the invention is to provide a wearing ring, which can in particular further reduce the risk of damage to the protective tube.
According to the invention, the set problem is solved by a wearing ring of the aforementioned type, which is characterized in that it has two layers, one of which coaxially surrounds the other.
As a result of the substantially coaxial layers of the wearing ring having different light absorption and therefore light reflection, i.e. different colours, after the wearing away of the outer layer, when then the lower layer is made visible by a different colour, it is easily possible to establish that the wearing ring has worn to such an extent that it must be replaced. The lower layer preferably has a reflecting power which is very noticeable, particularly e.g. bright red.
If, according to a preferred development, the layers engage in one another by means of ribs and grooves, it is easily possible to monitor the progression of the wearing of the wearing ring. As soon as the colour of the outer layer is no longer visible in the rib area thereof, the maximum wearing ring wear limit is reached. According to another preferred development, the outer layer, possibly with the exception of its ribs, has a constant, radial thickness. In particularly preferred manner, the layers are firmly interconnected and either the layers are firmly interconnected by a two-stage layer injection moulding process which welds together the layers or the layers are bonded together.
Alternatively, the layers may only be interconnected in frictionally engaging manner and in particular the layers are frictionally interlinked via their ribs and grooves.
For solving the inventive problem, in the case of a wearing ring it is also possible to provide it on its inside with at least four circumferential ribs. In that at least four ribs are provided on the inner circumference of the wearing ring, particularly on its inner layer, the latter can be used for connecting two tube parts, which are in each case held by means of two inner circumferential ribs of the wearing ring.
Then, advantageously, the wearing ring can be used as a coupling sleeve for two tube pieces, e.g. when using tube pieces having a differing elasticity.
For solving a further partial problem, the invention also provides for two half-shells forming the wearing ring to have an injection moulded inner thread and plastic screws engaging therein, the screws more particularly being made from polyamide. This obviates the use of metal parts for linking the two half-shells of the wearing ring, so that it is possible to prevent damage to robot parts rubbing along the wearing ring even when the plastics material has worn away to a significant extent, as disadvantageously occurs in the known wearing parts having metal screws.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.